U.S. patent number 9,065,310 [Application Number 14/048,092] was granted by the patent office on 2015-06-23 for belt conveyor and electromagnetic drive.
This patent grant is currently assigned to Laitram, L.L.C.. The grantee listed for this patent is Laitram, L.L.C.. Invention is credited to Kevin W. Guernsey, Wayne A. Pertuit, Jr., Bryant G. Ragan.
United States Patent |
9,065,310 |
Ragan , et al. |
June 23, 2015 |
Belt conveyor and electromagnetic drive
Abstract
A belt conveyor having an electromagnetic drive comprising a
rotor and a stator sealed in separate nonmagnetic and nonconductive
housings. The rotor is mounted to a drive shaft. A drive drum or
drive sprockets supported on the shaft have peripheral drive
surfaces that engage a conveyor belt. The rotor is coaxial with the
peripheral drive surface--either sealed within the drum or
sprockets or housed on the shaft axially spaced from the drive
surface. The rotor may include conductive rotor bars or permanent
magnets. The stator is spaced apart from the rotor across a narrow
gap and produces a traveling magnetic flux wave across the gap that
causes the rotor and the peripheral drive surface to rotate and
drive the conveyor belt.
Inventors: |
Ragan; Bryant G. (Metairie,
IA), Guernsey; Kevin W. (Destin, FL), Pertuit, Jr.; Wayne
A. (Westwego, LA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Laitram, L.L.C. |
Harahan |
LA |
US |
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Assignee: |
Laitram, L.L.C. (Harahan,
LA)
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Family
ID: |
50484331 |
Appl.
No.: |
14/048,092 |
Filed: |
October 8, 2013 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20140110227 A1 |
Apr 24, 2014 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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61715383 |
Oct 18, 2012 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02K
1/27 (20130101); H02K 7/14 (20130101); H02K
1/14 (20130101); B65G 23/08 (20130101); B65G
23/00 (20130101); B65G 23/23 (20130101); H02K
7/1008 (20130101); H02K 11/33 (20160101); H02K
17/165 (20130101) |
Current International
Class: |
B65G
23/08 (20060101); H02K 7/14 (20060101); H02K
7/10 (20060101); B65G 23/00 (20060101); B65G
47/10 (20060101) |
Field of
Search: |
;198/788,832,833,834,835 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0425021 |
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Jun 1993 |
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EP |
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1336956 |
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Nov 1973 |
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GB |
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1419358 |
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Dec 1975 |
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GB |
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H07-8331 |
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Feb 1995 |
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JP |
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10029715 |
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Feb 1998 |
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JP |
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10231009 |
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Sep 1998 |
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JP |
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9301646 |
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Jan 1993 |
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WO |
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0059810 |
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Oct 2000 |
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WO |
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2010121303 |
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Oct 2010 |
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WO |
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2012004770 |
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Jan 2012 |
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WO |
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2012075976 |
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Jun 2012 |
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WO |
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Other References
International Search Report and Written Opinion of the
International Searching Authority, PCT/US2013/063766, mailed Jan.
16, 2014, Korean Intellectual Property Office, Republic of Korea.
cited by applicant.
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Primary Examiner: Hess; Douglas
Attorney, Agent or Firm: Cronvich; James T.
Claims
What is claimed is:
1. A drive for a conveyor belt, comprising: a drive shaft having an
axis; a rotor mounted to the drive shaft; a drive element supported
by the drive shaft and having a peripheral drive surface coaxial
with the rotor, the peripheral drive surface adapted to engage a
conveyor belt; a stator separated from the rotor across a gap
extending partway around the rotor and producing a traveling
magnetic flux wave across the gap that interacts with the rotor to
cause the rotor to rotate the drive shaft and the peripheral drive
surface to drive an engaged conveyor belt.
2. A drive as in claim 1 wherein the rotor is enclosed within the
drive element.
3. A drive as in claim 1 wherein the peripheral drive surface
rotates through the gap between the rotor and the stator.
4. A drive as in claim 1 wherein the gap between the stator and the
rotor is great enough to admit a conveyor belt engaged with the
peripheral drive surface.
5. A drive as in claim 1 wherein the rotor includes
circumferentially spaced electrically conductive bars extending
axially along the drive element interior to the peripheral drive
surface.
6. A drive as in claim 5 wherein the electrically conductive bars
are backed by steel reaction bars to increase drive torque.
7. A drive as in claim 1 wherein the peripheral drive surface is
smooth.
8. A drive as in claim 1 wherein the peripheral drive surface has
drive faces circumferentially spaced at a regular pitch.
9. A drive as in claim 1 wherein the peripheral drive surface is
nonmagnetic and nonconductive.
10. A drive as in claim 1 wherein the rotor is sealed within the
drive element.
11. A drive as in claim 1 wherein the drive element is made of
plastic molded around the rotor.
12. A drive as in claim 1 further including a nonmagnetic and
nonconductive housing enclosing the stator.
13. A drive as in claim 1 wherein the rotor includes a plurality of
circumferentially spaced magnets.
14. A drive as in claim 13 wherein the poles of the magnets
alternate in polarity circumferentially around the rotor.
15. A drive as in claim 13 wherein each of the magnets is a Halbach
array.
16. A drive as in claim 1 wherein the rotor is an electrically
conductive aluminum cylinder interior to the peripheral drive
surface.
17. A drive as in claim 1 further comprising a plurality of drive
elements spaced apart axially and supported by the drive shaft.
18. A drive as in claim 1 wherein the rotor is axially spaced from
the drive element.
19. A drive as in claim 18 wherein the rotor is an electrically
conductive disc.
20. A drive as in claim 18 further comprising a wheel mounted on
the drive shaft axially spaced from the drive element and housing
the rotor.
21. A drive as in claim 1 further comprising a nonmagnetic and
nonconductive stator housing enclosing the stator and wherein the
drive element is nonmagnetic and nonconductive and encloses the
rotor.
22. A drive as in claim 1 wherein the stator includes a plurality
of circumferentially spaced poles having outer pole faces arranged
along an arc of a circle.
23. A drive as in claim 1 further comprising a motor controller
sending signals to the stator to control the traveling magnetic
flux wave and the rotation of the rotor.
24. A conveyor comprising: a drive shaft having an axis; a drive
surface rotated by the drive shaft about the axis; a conveyor belt
engaged by the drive surface to advance the belt; a rotor housing
made of a nonmagnetic and nonconductive material; a rotor sealed
within the rotor housing and coupled to the drive shaft; a stator
housing made of a nonmagnetic and nonconductive material; a stator
spaced apart from the rotor across a gap and sealed within the
stator housing, wherein the stator produces a traveling magnetic
flux wave across the gap that interacts with the rotor to cause the
rotor to rotate the drive shaft and the drive surface to advance
the conveyor belt.
25. A conveyor as in claim 24 wherein the drive surface is a
cylindrical outer surface of the rotor housing.
26. A conveyor as in claim 24 wherein the conveyor belt advances
through the gap between the rotor and the stator.
27. A conveyor as in claim 24 wherein the rotor includes
circumferentially spaced electrically conductive bars extending
axially along the rotor housing.
28. A conveyor as in claim 24 wherein the drive surface has drive
faces circumferentially spaced at a regular pitch and the conveyor
belt has drive faces engaged by the drive faces on the drive
surface, wherein the stator housing has a bearing surface bounding
the gap to force a drive face of the conveyor belt into engagement
with a drive face on the drive surface just ahead of the conveyor
belt's exit from the drive surface.
29. A conveyor as in claim 24 wherein the drive surface is formed
on a plurality of sprockets mounted at axially spaced positions on
the drive shaft.
30. A conveyor as in claim 24 wherein the conveyor belt does not
engage the drive surface in the gap between the stator and the
rotor and the conveyor further comprises a position limiter having
a bearing surface bearing against the conveyor belt to force it
toward the drive surface.
31. A conveyor as in claim 24 further comprising a motor controller
sending signals to the stator to control the magnetic flux wave and
the rotation of the rotor.
32. A conveyor as in claim 31 wherein the motor controller is
enclosed within the stator housing.
Description
BACKGROUND
The invention relates generally to power-driven conveyors and more
particularly to belt conveyors driven by separately housed stators
and rotors.
Conveyor belts are conventionally driven by sprockets, drums, or
pulleys mounted on a drive shaft rotated by an electric motor via a
reduction gear, a sprocket-chain system, or a belt-pulley system.
These standard components present many hiding places for debris and
other contaminants. In the food processing industry, the harboring
of contaminants and bacteria is problematic. Furthermore, reduction
gears wear out and require lubrication.
SUMMARY
A conveyor-belt drive embodying features of the invention comprises
a rotor mounted to a drive shaft having an axis. A drive element
having a peripheral drive surface is supported by the drive shaft.
The peripheral drive surface, which is adapted to engage a conveyor
belt, is coaxial with the rotor. A stator is separated from the
rotor across the gap that extends partway around the rotor. The
stator produces a traveling magnetic flux wave across the gap that
interacts with the rotor and causes it to rotate the drive shaft
and the peripheral drive surface to drive an engaged conveyor
belt.
In another aspect, a conveyor embodying features of the invention
comprises a drive surface rotated by a drive shaft about its axis.
A conveyor belt is engaged by the drive surface to advance the
belt. A rotor, sealed within a rotor housing, is coupled to the
drive shaft. A stator, spaced apart from the rotor across a gap, is
sealed within a stator housing. Both the rotor housing and the
stator housing are made of nonmagnetic and nonconductive materials.
The stator produces a traveling magnetic flux wave across the gap
that interacts with the rotor to cause the rotor to rotate the
drive shaft and the drive surface to advance the conveyor belt.
BRIEF DESCRIPTION OF THE DRAWINGS
These aspects and features of the invention, as well as its
advantages, are described in more detail in the following
description, appended claims, and accompanying drawings, in
which:
FIG. 1a is an isometric view of a stator usable in a conveyor-belt
drive embodying features of the invention;
FIG. 1b is an isometric view of one version of a drive system using
a stator as in FIG. 1a and a conductive-bar rotor in a drive
drum;
FIG. 1c is an isometric view of an alternative version of the drive
system of FIG. 1b with steel reaction bars backing the rotor bars
in the drive drum;
FIG. 1d is an isometric view of the drive system of FIG. 1b sealed
with end caps;
FIG. 2 is an isometric view of a conveyor system using a stator as
in FIG. 1a sealed in a housing under the drum and pressing against
the outer surface of a conveyor belt;
FIG. 3 is an isometric view of a conveyor system as in FIG. 2, but
with the stator sealed in a housing behind the drum;
FIG. 4 is an isometric view of a conveyor system as in FIG. 3 with
a dedicated position limiter;
FIG. 5 is an isometric view of a center-driven conveyor with a
stator as in FIG. 1a mounted in a housing below the belt
returnway;
FIG. 6 is an isometric view of a conveyor as in FIG. 5 with the
stator housing disposed above the returnway;
FIG. 7 is an isometric view of a conveyor with a drive system as in
FIG. 3;
FIG. 8a is an isometric view of a drive system as in FIG. 2, but
with sprockets, instead of a drum, housing the rotor;
FIG. 8b is an isometric view of a drive system as in FIG. 8a with
permanent magnets in the rotor;
FIG. 8c is an isometric view of a drive system as in FIG. 8b in
which the permanent magnets are arranged in Halbach arrays;
FIG. 9a is an isometric view of a sprocket-drive system as in FIG.
8a in which the rotor and stator are axially spaced from the drive
sprockets;
FIG. 9b is an isometric view of a sprocket-driven system as in FIG.
9a with a stator completely encircling the rotor;
FIG. 9c is an isometric view of a sprocket-driven system as in FIG.
9a in which the rotor is a conductive disc; FIG. 9d is an isometric
view of a sprocket-driven system as in FIG. 9a in which the rotor
is a conductive cylinder driven by a two-sided stator;
FIG. 9e is an isometric view of the stator end of the
sprocket-driven system of FIG. 9b with the rotor housing removed
from the housing for cleaning; and
FIG. 9f is an isometric view of a sprocket-driven system as in FIG.
9c with a conductive-disc rotor and in which a one-sided stator is
housed in a minimal housing.
DETAILED DESCRIPTION
A curved linear-induction stator usable in a belt-conveyor drive
embodying features of the invention is shown in FIG. 1a. The stator
10 has a core 12 which may be made up of a solid metal piece or
metal laminations. Poles 14 extend radially from the core to outer
pole faces 16 that define the arc of a circle. Coils 18 wrapped
around the poles 14 form electromagnets that are energized by an
alternating current to produce a magnetic flux wave through the
pole faces 16. The magnetic flux wave travels from pole to pole in
one direction or the other. (The coil on only one of the poles is
shown in FIG. 1a for clarity.)
Unlike the stators of most motors, the stator 10 in FIG. 1a does
not make a complete 360.degree. circle. Instead, it extends only
over an arc of about 90.degree.. In fact, the stator is more like a
curved linear-induction stator than a conventional motor
stator.
FIG. 1b shows the stator 10 of FIG. 1a associated with a rotor 20
consisting of a plurality of rotor bars 22 embedded in the interior
of a drive element, such as a drum 24, at regularly spaced
circumferential intervals. The rotor bars 22 are separated from the
stator pole faces 16 by a gap 26 that extends partway around the
rotor. The magnetic flux from the stator poles crosses the gap and
induces currents in the electrically conductive rotor bars that
produce a magnetic field that interacts with the stator field. The
resultant force causes the motor to rotate and chase the stator's
traveling magnetic field. The drum 24 has a smooth cylindrical
outer peripheral surface 28. Axial slots 30 in the outer surface at
a regular pitch form drive faces 32 that can drive drive-receiving
surfaces on a conveyor belt. Or the outer drive surface can be
smooth, uninterrupted by slots, for frictionally engaging and
driving a tensioned flat belt.
In FIG. 1c the rotor bars 22, which are preferably made of aluminum
or another electrically conductive material, are backed by torque
reaction bars 34, which may be made of a ferrous material, such as
steel, to increase the flux density and the drive force. (As used
throughout the description and claims, the terms "conductive" and
"nonconductive" refer to electrical conductivity.) As shown in FIG.
1d, the rotor is sealed within a rotor housing 36 formed by the
peripheral drive surface 28 and end caps 38 at each end of the
housing. The rotor housing is mounted on a drive shaft 40 extending
outward from the end caps. The rotor and the peripheral drive
surface are coaxial with each other and with the axis 42 of the
drive shaft. The peripheral drive surface is made of a nonmagnetic
and nonconductive material, such as plastic, so as not to interfere
with the traveling magnetic field or to have currents induced in
the drive surface.
FIG. 2 shows a belt drive with a rotor sealed within a rotor
housing 36 as in FIG. 1d. The stator is sealed within a nonmagnetic
and nonconductive stator housing 44. The stator housing has
generally smooth outer surfaces that are easy to clean. A conveyor
belt 46 has drive faces 48 along one side of regularly spaced teeth
50 formed on the inner side of the belt. The teeth are received in
slots 52 in the peripheral drive surface 28 of the drum 36. The
drive faces 32 bounding the slots engage the drive faces 48 to
advance the belt in the direction of belt travel 54. The conveyor
belt 46 passes through the gap 26 between the stator housing 44 and
the rotor housing 36. The stator housing 44 presents a concave
bearing surface 47 against the conveyor belt to ensure that a drive
face 48 of the belt is engaged by a drive face 32 of the drum 36 at
a position just ahead of the exit point 56 of the belt from the
drum. In this way, the stator housing also serves as a position
limiter for a low-tension, positively driven conveyor belt.
FIG. 3 shows a stator housing 58 mounted behind the rotor drum 36.
In this configuration, unlike that of FIG. 2, the belt 46 does not
pass through the gap 26. For this reason, the gap can be narrower,
which improves the coupling of magnetic flux from the stator to the
rotor. Furthermore, the stator housing 58 could be formed as an
extension of the conveyor carryway. The stator housings 44, 58 in
FIGS. 2 and 3 each have arms 60, 61 that attach to the drive shaft
40 to maintain a fixed gap width between rotor and stator. Because
the stator housing 58 in FIG. 3 does not contact the belt 46, its
concave face 62 cannot serve as a position limiter. A modified
version of the stator housing in FIG. 3 is shown in FIG. 4 with a
position limiter 64 attached to distal ends of the arms 61 of the
stator housing 58. The concave inner surface 66 of the position
limiter bears against the belt 46 and maintains the belt tooth 50
engaged with the drive face 32 of the drum 36 just ahead of the
exit point 56 of the belt from the drum. The position limiter 64 is
connected to the arm 61 by legs 68.
FIGS. 5 and 6 show conveyor belts 46 driven by a drive unit in the
returnway, rather than at an end of the carryway as in FIGS. 2-4.
In FIG. 5 the stator housing 70 is mounted below the drum 36 with
the belt passing through the stator-rotor gap 26. In FIG. 6 the
stator housing 70' is mounted above the drum 36, and the belt 46
does not advance through the narrower gap 26'. The stator housing
70' can be integral to the carryway. Snubber rollers 72 before the
entrance and after the exit to the drum increase the
circumferential extent of belt wrap around the drum.
FIG. 7 shows a complete conveyor system, in which a stator housing
58 as in FIG. 3 is mounted at an end of the carryway. A motor
controller 74 sends motor control signals over signal lines 76 to
the stator in the housing 58 to control the magnetic flux wave, the
rotation of the rotor and the drum 36, and the belt speed and
direction. The motor controller 74' could alternatively be mounted
within the stator housing 58, as shown in FIG. 3, requiring only
the connection of ac line power. The motor controller could be
operated and monitored remotely via a wireless RF link 75 or other
remote control means. This would further improve the hygienic
qualities of the conveyor.
Instead of using a drum as the driving element and rotor housing,
the electromagnetic drives in FIGS. 8a-8c use narrower sprocket
wheels to house the rotors. In FIG. 8a the rotor comprises a series
of electrically conductive plates 78 embedded in nonmagnetic and
nonconductive sprockets 80 mounted on a drive shaft 82. The outer
peripheral surfaces 84 of the sprockets engage and drive the
conveyor belt 46. Like the conductive rotor bars in FIG. 1c, the
conductive plates 78 can be backed by steel plates to reduce
reluctance in the magnetic circuit between the stator and rotor. In
the rotor configuration of FIG. 8a, the electromagnetic drive, like
the drives in FIGS. 1b and 1c, operates as an ac induction
motor.
The sprockets 86 in FIG. 8b contain permanent magnets 88
alternating circumferentially in polarity between outward north
poles N and south poles S. In the sprockets 90 in FIG. 8c, the
magnets are arranged as Halbach arrays 92 of alternating polarity
to concentrate the magnetic flux in the direction of the stator
poles. The permanent magnet rotors of FIGS. 8b and 8c and the
stators can be operated as permanent-magnet ac motors or as
brushless dc motors, as could drum versions that contain permanent
magnets in the rotors.
In FIG. 9a the rotor is sealed in a rotor housing 94 in the form of
a wheel axially remote from standard sprockets 96 mounted on a
drive shaft 98. The sprockets 96 have peripheral drive surfaces
that engage the conveyor belt. The stator is sealed in a stator
housing 100 that extends partway around the circumference of the
embedded rotor. In FIG. 9b the stator in a stator housing 102
completely encircles the rotor wheel 94 to form a conventional
motor, but with the rotor and stator sealed in separate housings.
In both these examples the rotor could include electrically
conductive plates like those in the sprockets of FIG. 8a or
permanent magnets like those in FIGS. 8b and 8c. The motor formed
by the rotor and stator has a single bearing 103 and requires no
shaft coupler or reduction gear. And, as shown in FIG. 9e, the
rotor housing 94 can be slid along the drive shaft 98 away from the
stator housing 102 for easy cleaning of both.
In FIG. 9c the electromagnetic drive is axially remote from the
drive elements as in FIGS. 9a and 9b, but the rotor is a sealed
conductive disc 104 mounted on the drive shaft 98. The stator is
shown as a double-sided stator sealed in a stator housing 106 that
extends partway around the periphery of the disc. The double-sided
stator improves the coupling of magnetic flux to the disc rotor.
But a single-sided stator could be used to rotate the disc 104, as
shown in FIG. 9f, in which a minimal stator housing 107 is used for
easy cleaning.
In FIG. 9d a rotor drum 108 has an extension 110 that extends
axially outward of its peripheral drive surface 112. A conductive
cylinder in the extension serves as a rotor that is rotated by the
magnetic flux wave produced by a two-sided stator sealed in a
stator housing 114 that extends partway around the rotor. A
one-sided rotor could be used as well.
Although the invention has been described with reference to a few
exemplary versions, other versions are possible. For example, the
drive systems shown with sprockets could be used with drums, and
vice versa. As another example, the rotor need not be mounted on
the drive shaft and can be coupled to the drive shaft other than
through a direct connection. For example, the rotor can be coupled
to the drive shaft via a reduction gear, a sprocket-chain system,
or a belt-pulley system. And, although all the drive systems
described in detail have constant-width stator-rotor gaps, the gap
width does not have to be constant. For example, a curved rotor
could be used with a linear stator tangent to the rotor or with a
curved liner stator having a much greater radius of curvature than
the rotor and a diverging air gap. So, as these examples suggest,
the claims are not meant to be limited to the versions described in
detail.
* * * * *